One type of printing device that is widely known is a thermal tape printer. A thermal tape printer generally comprises a printing means comprising a thermally activatable printhead for printing onto an image receiving tape. Typically, the image receiving tape has an upper layer for receiving an image and a removable liner layer or backing layer secured to the upper layer by a layer of adhesive, such that after an image has been printed the liner layer or backing layer can be removed and the image receiving tape can be stuck down in the form of a label. Such thermal printers often include cutters for cutting off a length of image receiving tape after the image has been printed. Such thermal printers operate with a consumable in the form of image receiving tape, or any other image receiving substrate such as heat shrink tube, magnetic, iron-on labels, plastic strips, etc. The term “consumable” is used herein to denote any appropriate form of providing image receiving tape. The image receiving tape may comprise a continuous backing sheet whilst the image receiving layer has been pre-cut into labels, such that a label can be printed and then peeled off from the backing sheet. A printer intended to operate with such an image receiving tape does not need a cutter to cut the image receiving tape.
A number of forms of consumables are known in the art, including cassettes or cartridges which comprise a housing in which is located a supply of image receiving tape. Cassettes are generally usable once only, such that once the image receiving tape has been consumed, the cassette (including the housing) is thrown away.
A cassette can have a housing which substantially encloses the supply of image receiving tape or the housing can be simpler, for example a spool and two sides within which the tape is located. A simpler cassette is sometimes called an image receiving holder.
Another type of consumable is a roll of tape without a permanent holder, for example wound on a paper core. These are termed “supplies”.
In thermal printers, an image is generally generated by activation of a thermal printhead against an ink ribbon, such that ink from the ink ribbon is transferred onto the image receiving tape at a print zone. So-called direct thermal tapes are also available, in which an image is created directly onto the direct thermal tape without the interposition of an ink ribbon. If an ink ribbon is used in a thermal printer, it is generally provided held in a cassette having a housing, the housing being insertable into the printer. The ink ribbon is passed out of the cassette into overlap with the image receiving tape such that both the ink ribbon and the image receiving tape are fed past the printhead. Each length of ink ribbon is used for only one printing operation and is then rewound back into the ink ribbon cassette. The ink ribbon is therefore also a consumable.
Known tape printing apparatus of the type with which the present invention is concerned are disclosed in EP-A-322918 and EP-A-322919 (Brother Kogyo Kabushiki Kaisha) and EP-A-267890 (Varitronic). The printers each include a printing device having a cassette receiving bay for receiving a cassette or tape holder. In EP-A-267890, the tape holder houses an ink ribbon and a substrate tape, the latter comprising an upper image receiving layer secured to a backing layer by an adhesive. In EP-A-322918 and EP-A-322919, the tape holding case houses an ink ribbon, a transparent image receiving tape and a double sided adhesive tape which is secured at one of its adhesive coated sides to the image tape after printing and which has a backing layer peelable from its other adhesive coated side. With both these apparatus, the image transfer medium (ink ribbon) and the image receiving tape (substrate) are in the same cartridge.
It has also been proposed by the present applicants in, for example, EP-A-578372 to house the ink ribbon and the substrate tape in separate cassettes or cartridges.
In all of these cases, the image receiving tape passes in overlap with the ink ribbon to a print zone consisting of a fixed print head and a platen against which the print head can be pressed to cause an image to transfer from the ink ribbon to the image receiving tape. There are many ways of doing this, including dry lettering or dry film impression, but the most usual way currently is by thermal printing where the print head is heated and the heat causes ink from the ink ribbon to be transferred to the image receiving tape.
The devices of the type described above are provided with a keyboard which enables a user to enter characters, symbols and the like to form an image to be printed by the tape printer. The keyboard usually has text character keys and number keys for entering letters and number keys respectively, plus some function keys which, among other things, operate menus and allow printing attributes to be set.
Cassettes are usually made from plastics material and for practical purposes are often formed from more than one moulded part. One problem with such cassettes is that they can be costly to manufacture because each moulded part is relatively complex in order to achieve correct placement and unwinding of the image receiving medium, and the parts need to be fitted together by a manufacturing process e.g. welding. It would be desirable to provide a cassette made from parts which can be press-fit or snap-fit together.
Another problem with such cassettes is that excessive unwinding of the tape from the cassette can occur, and this is undesirable. This can happen during transportation of the cassette, but can also occur during operation of the printer when the tape is being driven. It would be desirable to provide a cassette with means for preventing excessive unwinding of the tape.
During use of a cassette, image receiving tape contained therein must be unwound and must exit the cassette in order to be printed on. It is vital that the tape is properly aligned in the correct position relative to the printhead and, if used, the ink ribbon. Although this may be in part achieved by guiding elements within the printer, these may not be able to achieve accurate alignment if the tape is not correctly aligned when it arrives at the guiding elements. One problem with existing cassettes is that it is possible for the image receiving tape to move laterally during unwinding and exit from the cassette, and if enough lateral movement is accumulated over the unwinding and exit path, the image is not printed centrally on the tape or, in the worst case, does not even fit on the tape due to being printed in the wrong position or due to folds in the tape. It would therefore be desirable to provide a cassette which has means for ensuring correct alignment of exiting image receiving tape.
A printer of the type previously described is often useable with different widths of tape. This enables the creation of many different sizes of labels. It is usual to size a cassette housing to correspond to the width of the tape contained in the cassette, thereby giving a visual indication of the tape size and avoiding use of unnecessarily bulky cassette housings. Having a suitably sized casing may also make it easier for tape to exit the cassette correctly aligned, depending on the design of the cassette and printer. One problem associated with the provision of multiple cassettes is the manufacturing cost for making the various designs. It would be desirable to mitigate these costs.
As well has having different cassettes of different tape width available, it is also common to provide various cassettes of different colours and styles of tape. Another consequence of having different cassettes available for use with a printer is that a user or multiple users will want to use different cassettes but not use all the tape on one cassette at once. Therefore, one cassette will be removed by a user and another inserted. A problem associated with this is wastage of tape. This occurs because after creation of a label, a certain amount of further tape has exited from the cassette and is in the region between the cassette and the printer tape exit. It would be desirable to rewind this further tape prior to removal of a cassette so that it is available for use the next time the cassette is inserted into the printer.
In order to achieve successful printing the image receiving cassette must be held firmly in place in the printer and must be inserted in the correct location. If the cassette can move about within the printer or is incorrectly positioned during insertion, images will not be correctly printed on the tape, or malfunction of the printer could be caused. It would therefore be desirable to provide means for ensuring accurate alignment and positioning of a cassette in a printer and means for retaining the cassette in the correct position after insertion.
Most printers include a drive means which rotates a supply spool of a tape cassette, thus feeding tape to the printing area. It may be desirable to provide a further means of locally feeding the tape in the printing area.
Another requirement for successful printing is that the ink ribbon cassette is correctly inserted in the printer and is retained in the correct location. If the ribbon cassette can move about within the printer it may result in incorrect feeding of the ink ribbon and hence a lack of proper transfer of ink to the image receiving tape during printing. It would therefore be desirable to facilitate correct insertion of the ink ribbon cassette and to ensure retention of the ink ribbon cassette in the correct position in the printer.